Sensoaesthetic Materials

About

At the Institute of Making, we are actively conducting research into developing a sensoaesthetic theory of materials. Materials science concerns itself with the physical characterisation of materials, while artists and designers are generally much more interested in the aesthetic side of materials. Applying scientific methodology to the study of the aesthetic, sensual and emotional side of materials – their sensoaesthetic properties - may improve our understanding of how people interact with materials, and may lead to more innovative and multisensory design. In developing a sensoaesthetic theory of materials we aim to forge links between these two material domains.

Background

There is a huge amount of technical information about materials available for scientists, technologists and industrialists to use in their work. Although this information tells us a great deal about the physicality of materials, it sheds very little light on their sensoaesthetic properties. In fact, there is has been very little work which has looked at how the physical properties of materials relate to their sensual and aesthetic properties. Within the world of materials, there exists a big split between the materials science community, those scientists, technologists and industrialists who are interested in the physicality of materials, and those in the materials-arts community who are interested in the sensoaesthetic properties of materials. The two sides do not speak a common language. The overall aim of our research is to attempt to fill in this gap by using scientific methods to study those properties of materials which are largely ignored by materials scientists, yet are vitally important to the materials-arts community.

The sensoaesthetic properties are strongly dependent on perception, and the study of perception falls within the realm of psychology. Psychophysics - the ‘science of the senses’ - is a branch of psychology that uses quantitative measurement techniques to study sensation and perception. Our research directly combines psychophysics with materials science. At first, it may seem that a hard scientific discipline may not shed too much light on the softer side of materials. However, upon closer inspection it becomes obvious that the way we interact with materials, and the sensations and emotions we feel from them, is rooted in their fundamental physical properties.

Our advanced sense of materiality is something we take for granted. Everyone has a huge amount of materials knowledge which they use in all of their interactions with the physical world around them. Your mind is like a database of sensory experiences, and when you come into contact with something your brain pieces together all relevant information and tells you what’s going on. Through your sense of touch, smell, taste, hearing and vision you can amass a huge amount of accurate information very quickly. What your sense are detecting are actually the physical properties of the materials, and it those same physical properties which materials science measures and explains. For example, metals generally feel cool to the touch because they conduct heat away from your skin very quickly. So we can say that, in general, materials with high thermal conductivity will feel cool to the touch. Or if an object is soft to the touch, then we can look at physical variables such as elastic modulus or plasticity to characterise the interaction.

Our current area of research is around the area of the touch of materials. The central question in our research into the touch of materials is how the perception of materials relates to their physical properties. Our research methods contain strong elements of both psychophysics and materials science, which we use to probe both the psychological and physical aspects of touch perception. The sense of touch is a hugely important part of our interaction with the world around us. Through touch, we can very quickly discern a lot of details about a material. The mind is like a database of sensory experiences, and as it pieces together sensory information it builds up our sensorial perceptions. This process is governed by the neurophysical make-up of your body and brain on a physical level, but your emotions and aesthetic tastes play a big part as well. In our work, we make measurements of people’s sensoaesthetic perception of a range of different materials through their sense of touch, and the results back to the core physical properties of the materials as described by materials science.

Sounds and their cultural resonances are built upon material relationships that produce specific acoustic effects and connotations. The aesthetic qualities and scientific properties of sounds and our perception of them, is key to our understanding of the world around us, and the relationships we build with materials.

To test the comparative acoustic properties of different materials we made a set of tuning forks of identical shape from varying materials. The three principle factors that influence the production of sound by a tuning fork are the shape, the density and the elastic modulus of the material from which the fork is made. The qualities of the sound produced by a tuning fork are experienced as a note of a specific pitch (frequency), with a particular brightness (a combinatory factor of duration and amplitude). Ashby and Johnson plotted the theoretical relationship between the acoustic pitch and the acoustic brightness of a wide range of materials in their multidimensional scaling (MDS) map of acoustic properties [1]. We used the tuning forks to investigate the effects of materiality on sound, with exact frequency produced by each fork measured and the shift in pitch attributed to the change in materials. The tuning forks were also played and assessed by musicians whose perceptions of pitch and brightness were judged against those of the MDS.

In terms of the frequencies produced by the tuning forks, we found broad agreement with the theoretical predictions, apart from a few anomalies. We also found that judgements of pitch made by musicians were also in agreement with the frequency measurements. The greatest surprise was that the pitch of disparate materials could be very similar, whilst the brightness of the note varies dramatically, due to variations in materials coefficient of loss.

Research on the taste of materials was conducted to address the question of what physical properties of materials can be correlated with the senso-aesthetic properties that define our experience of taste.

Tastes are received through our taste buds, which are located on the upper surface of the tongue. There are five basic tastes: bitter, salty, sour, sweet, and umami, although ‘fat’ is also now becoming a candidate for distinct taste sensation. These tastes are not the only component of the sensations associated with the mouth; other important factors include smell, detected by the nose, texture detected by mechanoreceptors, and temperature, detected by thermoreceptors [1] . The chemical aspects of taste of inedible materials, such as those we considered in our experiment, are often discussed in terms of their reduction potential, in other words their susceptibility to being oxided in the mouth. These potentials have been measured for most materials, and confirm broad trends of taste, which is that metals like copper and aluminum taste strong, whereas metals gold and silver are almost tasteless (hence the high status of silverware cutlery). There are plenty of exceptions (such as titanium) and there had been no previous systematic investigation of the relation between perceived taste, and physical or chemical properties.

With this is mind we conducted experiments in which we asked volunteers to take spoons which had been coated with seven different types of metal: zinc, copper, stainless steel, gold, tin, chrome, silver.